Add visual IconSelect grid for filter type picker in PP template editor

Replace plain filter type dropdown with icon grid showing each filter
with its icon and description. Selecting a filter immediately adds it
to the template (no separate "+" click needed).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/wled_controller/static/locales/zh.json

@@ -382,17 +382,29 @@
   "filters.drag_to_reorder": "拖动以重新排序",
   "filters.empty": "尚未添加滤镜。使用下方选择器添加滤镜。",
   "filters.brightness": "亮度",
+  "filters.brightness.desc": "调整整体图像亮度",
   "filters.saturation": "饱和度",
+  "filters.saturation.desc": "增强或降低色彩强度",
   "filters.gamma": "伽马",
+  "filters.gamma.desc": "非线性亮度曲线校正",
   "filters.downscaler": "缩小",
+  "filters.downscaler.desc": "降低分辨率以加快处理",
   "filters.pixelate": "像素化",
+  "filters.pixelate.desc": "马赛克式块平均",
   "filters.auto_crop": "自动裁剪",
+  "filters.auto_crop.desc": "移除信箱式内容的黑边",
   "filters.flip": "翻转",
+  "filters.flip.desc": "水平或垂直镜像翻转",
   "filters.color_correction": "色彩校正",
+  "filters.color_correction.desc": "白平衡和色温调整",
   "filters.filter_template": "滤镜模板",
+  "filters.filter_template.desc": "嵌入另一个处理模板",
   "filters.frame_interpolation": "帧插值",
+  "filters.frame_interpolation.desc": "帧间混合以获得更平滑的输出",
   "filters.noise_gate": "噪声门",
+  "filters.noise_gate.desc": "抑制低于阈值的细微色彩变化",
   "filters.palette_quantization": "调色板量化",
+  "filters.palette_quantization.desc": "将颜色减少到有限调色板",
   "postprocessing.description_label": "描述（可选）：",
   "postprocessing.description_placeholder": "描述此模板...",
   "postprocessing.created": "模板创建成功",